This invention relates to a composite building module which is similar to monolithic cast concrete modules in outward appearance and use, yet has significant improvements in insulating properties and weight reduction. More particularly, this invention relates to a composite building module having a rigid foam core, such as a rigid urethane polymer foam, encased in a shell made of a hardened mixture of cement and fibers, such as glass fibers.
Because of increased costs in material and labor, the construction industry has come to use prefabricated building modules, for example wall panels, roof decks and the like. A popular form of construction is known as "curtain-wall" construction and involves the use of a structural steel skeleton to which prefabricated or precast panels are attached. Such curtain-wall panels are commonly cast from reinforced concrete and are provided with a surface finish such as a smooth concrete finish or aggregate imbedded into the face of the panels. These panels are extremely heavy, for example a 4 .times. 8 curtain-wall panel cast from reinforced concrete weighs from 1400-1600 lbs., and requires heavy construction equipment to install. In addition, these panels provide very poor insulating properties and by themselves are a poor vapor barrier. This necessitates further construction to insulate and seal the stacked-up curtain-wall of precast concrete modules.
The construction industry has long sought improved building elements that will offer advantages in material and construction costs.
The present invention provides a monolithic-like building module which is extremely light in weight as compared to precast concrete panels for example, and which has greatly improved insulating and vapor barrier properties per se. Because the present invention utilizes an in situ foamed core, an adhesive interlock between core and shell is formed which is stronger than either material by itself. The chemical foaming reaction that takes place, plus the fact that foaming takes place in an enclosed shell under retention, results in an overall intimate adhesive interlock and a prestressed structure wherein the shell is under tension and the core is under compression. This means that the shell and core are now united together into a monolithic-like structure that has far greater strengths (because of the overall adhesive interlock) than prior laminated panels using preformed foam plastic cores, and, at the same time, is light in weight and has excellent insulating and vapor barrier properties.